CNN  —  For the past two years, summer in Spain has meant prominent protests against tourism: holidaymakers being drenched by angry locals armed with water pistols in Barcelona and protesters marching under banners proclaiming “Your paradise is our nightmare” in the Balearic Islands regularly make headlines as the saturation of the summer season gets underway. Tourism is a pillar of Spain’s economy, contributing over 12% to the national GDP . But in destinations where cruise ships constantly